The investigators plan to examine the effect of a lipid infusion on TLR4 expression and insulin sensitivity. A group of 30 subjects aged 18-60 years old, lean (BMI < 26 kg/m2) normal glucose tolerant subjects without a family history of type 2 diabetes will receive a lipid or saline infusion. The subjects will be randomly assigned to first receive either a 48 hour long lipid or saline infusion. Approximately 4-6 weeks later subjects will return to undergo another study (if, in the first study they received lipid, on the second study they will receive saline, and vice versa). A near-equal number of women and men will be included in each group.